West Valley Fault

Its Nature and Possible Risks in the Community

The West Valley Fault is 100 kilometers in length and traverses the cities of Metro Manila namely Taguig, Muntinlupa, Paranaque, Quezon City, Pasig, Makati, and Marikina as well as nearby provinces of Rizal, Laguna, Cavite, and Bulacan. These places will suffer greatly and the outcome would be devastating the moment this fault moves.


It is said that it last moved on the year 1658 and experts warn that a major quake along the fault line can cause 50,000 deaths if residents aren’t prepared.


The West Valley Fault, which traverses various parts of Metro Manila and surrounding provinces, is expected to greatly affect the country since the region is not only highly populated, it also hosts the seat of government and the country’s business capital. According to the Metropolitan Manila Earthquake Impact Reduction Study (MMEIRS), a 7.2-magnitude earthquake from the West Valley Fault will result in the collapse of 170,000 residential houses and the death of 34,000 people. Another 114,000 individuals will be injured while 340,000 houses will be partly damaged.


The fault, which has moved 4 times in the last 1,400 years, moves roughly every 400 years, according to Philvocs Director Renato Solidum. The last major earthquake generated by this fault was in 1658, or 357 years ago. This means the metro is already due for the next big quake.



At the time the MMEIRs study was conducted, there were 1,325,896 residential buildings, 981 mid-rise buildings, 119 high-rise buildings, and 1,826 public-purpose buildings. Public-purpose buildings at the time included hospitals (177), schools (1,412), fire stations (124), police stations (43), city and municipal halls (53).


Of these, the study projected, residential buildings would sustain bulk of the damage from the

earthquake. Details of damage projections below:

  • Residential buildings – 339, 800 (25.6%) partly damaged; 168,300 (12.7%) heavily damaged

  • Mid-rise buildings (10-30 stories) – 27% partly damaged, 11% heavily damaged

  • High-rise buildings (30-60 stories) – 2% heavily damaged, 12% partly damaged

  • Public-purpose buildings – 8-10% heavily damaged, 20-25% partly damaged

The quality of construction and the type of building materials used play a big role in a building’s chances of surviving the earthquake, according to experts at Philvocs.

While Metro Manila is said to be the most developed place in the country, it appears to be the most dangerous and uninhabitable city when a catastrophic earthquake strike. In one of the plenary presentations of the 17th Science Council of Asia Conference, hosted by the National Research Council of the Philippines or NRCP in June 2017 at the Philippine International Convention Center, Dr. Renato U. Solidum, Jr., DOST Undersecretary for Disaster Risk Reduction and Climate Change Adaptation, said that when the West Valley Fault moved and generated a 7.2 magnitude earthquake, 34,000 people may die and will damage lifelines including water, infrastructure, roads, ports, and telecommunication.